Three heads are not always better than one.

With hitting coach Eric Chavez, pitching coach Jeremy Hefner and player development coordinator Dick Scott managing in place of the absent Buck Showalter, no one stopped Starling Marte from running the Mets out of a potential late rally Thursday in a 5-2 loss to the Giants.

Marte was cut down trying to steal second base to end the seventh inning, taking a hot bat out of Francisco Lindor’s hands with runners on the corners.

“I always have the green light,” Marte said through a translator. “I thought that was an opportunity to take the bag there. I wanted to be aggressive. I went, but they called me out.”

The Mets trailed 5-0 until Marte’s two-out bloop RBI single into the triangle in right-center field. But the makings of a potential rally were foiled by a bad fundamental play — even with the speed of a 50-base stealer.

Hefner, the only one of the co-managers available to the media after the game, said Marte’s green light was a better question for the other two.

“I don’t have any regrets,” Marte said. “Everyone knows, the type of player I am, I was going to go in a situation like that. I wanted to get in a better position to score on a hit.”

Showalter and his master’s degree is expected to return to the dugout Thursday after he underwent an undisclosed medical procedure. His voice from a Thursday morning conversation about “normal” pregame talking points was on the minds of his deputies — all the way through the coaching staff — when managing got advanced in the eighth inning.

“You have a lot of guys with a lot of experience in that dugout,” Hefner said. “There was no question that we were going to be able to navigate the game and talk through things. Obviously, we missed Buck and his leadership, but given the circumstances, we did a good job.”

The Mets lined up three straight pinch hitters after putting runners on first and second with one out in the eighth. Robinson Cano grounded out, with both runners advancing one base, and Dom Smith lined a would-be two-run double that was robbed by leaping third baseman Wilmer Flores.

“Firing Dom and Robby in that situation was important against their tough righty,” said Hefner, who was tasked with figuring out which reliever to go when the Mets were a “home run away from [it] being a really close game” in the eighth.

Jeff McNeil was on deck when the inning ended, but went to third base to start the ninth. The decision was to insert McNeil into Smith’s place in the lineup (originally Luis Guillorme’s) and have him due up ninth rather than have him replace James McCann, as he would’ve if Smith’s line drive had found a hole.

“That’s baseball,” Smith said. “Sometimes you hit it and it finds grass. Sometimes you hit it right at people.”

It appeared Marte grounded into a game-ending double play, but the Mets’ committee challenged the out at first base and forced a reversal. That replay review was a win — but it only delayed a loss.